Field
One or more example embodiments of inventive concepts relate to semiconductor devices, and more particularly, to semiconductor memory devices having a separate source line structure.
Description of Related Art
In general, semiconductor memory devices may be classified as nonvolatile memory devices and volatile memory devices.
A magnetic random access memory (MRAM) is a resistive memory, which is a type of nonvolatile semiconductor memory device, in which stored data is retained even if supply of power to the MRAM is stopped. In a MRAM, a data value stored in a cell thereof is determined according to whether a resistance value is high or low.
A spin torque transfer-magnetic random access memory (STT-MRAM) is referred to as a universal memory device, which may have the relatively low price of a dynamic random access memory (DRAM), while also having the relatively high memory capacity and relatively high operating speed of a static random access memory (SRAM), and nonvolatile characteristics of a flash memory.
A bit-line sense amplifier (BLSA) is needed to operate the STT-MRAM at relatively high speeds.
In the case of a STT-MRAM, chip size and a write voltage may vary according to an arrangement of source lines. In this regard, the number of source lines to be arranged may be reduced to reduce the chip size.
A nonvolatile semiconductor memory device having a common source line structure is relatively small in chip-size overhead, but requires a relatively high write voltage and a repair operation in which a defective memory cell is replaced with a spare memory cell.
Furthermore, in a nonvolatile semiconductor memory device having a separate source line structure, chip-size overhead is relatively high since source lines are respectively provided for all bit lines.